1. Field of the Invention
The present invention generally relates to a live roller conveyor employing transport or carrier rollers rotatably supported from a frame to define a load bed and, more particularly, structural arrangements for effectively controlling rotation of the rollers by providing a unique friction drive train which make three distinct categories of conveyors, namely, live roller conveyors, minimum pressure accumulation conveyors, and zero pressure accumulation conveyors.
2. Description of the Prior Art
Conveyors employing rollers have been used in conveying various loads for many years and generally include a plurality of rotatable transport rollers which are driven in a manner to convey the load in a desired direction with the driving connection with the rollers being such to enable the load on the load bed, such as a plurality of boxes or other items, to stop and accumulate without adverse effect on the load or on the conveyor.
Prior U.S. Pat. No. 1,903,732, issued Apr. 11, 1933, discloses such a conveyor in which a generally wide, flat drive belt underlies the transport rollers with pressure rollers underlying the drive belt and oriented in staggered relation to the transport rollers so that upward pressure on the drive belt will maintain it in frictional driving engagement with the transport rollers. Another example of the development in this field is found in U.S. Pat. No. 3,563,365, issued Feb. 16, 1971, in which the belt underlying the transport rollers is in the form of a relatively narrow V-belt engaged by underlying pressure rollers with the V-belt oriented at one side of the conveyor. U.S. Pat. No. 3,650,375 issued Mar. 21, 1972, discloses a live roller conveyor in which the rollers are driven by independent belts all driven from a single line shaft. Many other patents have been issued covering conveyors of this type with most of the patents being directed to solutions to the problem of maintaining a constant drive force on the transport rollers. Installational requirements for such conveyors vary quite widely and while accumulating conveyors have received substantial acceptance and are used extensively, the problem of maintaining a controlled driving force on the transport rollers remains a problem as does the installational flexibility.